Method of forming a transistor gate of a recessed access device, method of forming a recessed transistor gate and a non-recessed transistor gate, and method of fabricating an integrated circuit

Abstract

Methods and structures are provided for full silicidation of recessed silicon. Silicon is provided within a trench. A mixture of metals is provided over the silicon in which one of the metals diffuses more readily in silicon than silicon does in the metal, and another of the metals diffuses less readily in silicon than silicon does in the metal. An exemplary mixture includes 80% nickel and 20% cobalt. The silicon within the trench is allowed to fully silicide without void formation, despite a relatively high aspect ratio for the trench. Among other devices, recessed access devices (RADs) can be formed by the method for memory arrays.

1. A method of forming a gate of a recessed access device, comprising:
 forming a trench within semiconductive material of a substrate, the trench having a top width that is less than 60 nm; 
 depositing gate material comprising polysilicon to within the trench; 
 depositing a metal layer over the semiconductive material, over the polysilicon and within the trench, the metal layer comprising at least two different metals, the two different metals having opposing diffusivities relative to silicon; 
 subjecting the polysilicon and the metal layer to a silicidation anneal to form metal silicide within the trench; and 
 forming an insulator over the metal silicide. 
 
     
     
       2. The method of  claim 1  wherein the silicidation anneal transforms all of the polysilicon to metal silicide. 
     
     
       3. The method of  claim 1  wherein the silicidation anneal forms the metal silicide at the bottom of the trench. 
     
     
       4. The method of  claim 1  wherein the two different metals comprise nickel and cobalt. 
     
     
       5. The method of  claim 4  wherein the metal layer has less cobalt than nickel. 
     
     
       6. The method of  claim 1  wherein one of the two different metals comprises at least one of Ni, Pt, and Cu, and another of the two different metals comprises at least one of Co, Ti, and Ta. 
     
     
       7. The method of  claim 6  wherein the two different metals comprise nickel and titanium. 
     
     
       8. The method of  claim 6  wherein the two different metals comprise nickel and tantalum. 
     
     
       9. The method of  claim 6  wherein the two different metals comprise platinum and cobalt. 
     
     
       10. The method of  claim 6  wherein the two different metals comprise platinum and titanium. 
     
     
       11. The method of  claim 6  wherein the two different metals comprise platinum and tantalum. 
     
     
       12. The method of  claim 6  wherein the two different metals comprise copper and cobalt. 
     
     
       13. The method of  claim 6  wherein the two different metals comprise copper and titanium. 
     
     
       14. The method of  claim 6  wherein the two different metals comprise copper and tantalum. 
     
     
       15. The method of  claim 1  comprising recessing the metal silicide within the trench. 
     
     
       16. The method of  claim 15  comprising after recessing the metal silicide within the trench, forming the insulator within the trench over the metal silicide.